Copper molybdate catalyst, preparation method, application and method for producing 4-propylphenol
A copper molybdate catalyst was prepared by mixing water-soluble molybdate and copper salt in water for the demethoxylation reaction of 4-propylguaiacol. This method solves the problems of complex catalyst preparation and low efficiency in the prior art and achieves the effect of high-efficiency production of 4-propylphenol.
Patent Information
- Application Number
- CN202410920737.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-10
- Publication Date
- 2026-01-13
AI Technical Summary
Existing methods for preparing copper molybdate catalysts are complex, environmentally unfriendly, and economically unfeasible. The demethoxylation reaction of 4-propylguaiacol has low efficiency, making it difficult to produce 4-propylphenol efficiently.
A copper molybdate catalyst was prepared by mixing water-soluble molybdate and water-soluble copper salt in water, followed by vacuum rotary evaporation and calcination. This catalyst was used for the demethoxylation reaction of 4-propylguaiacol in a fixed-bed reactor. The reaction conditions were mild, and water was used as the solvent, which simplified the operation and improved the catalytic performance.
The prepared copper molybdate catalyst exhibits high conversion rate, good product selectivity, strong stability, mild reaction conditions, high feed conversion rate, and high product selectivity, avoiding the shortcomings of using precious metals and solvents.
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Figure CN121314599A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to a copper molybdate catalyst, a preparation method, an application and a method for producing 4-propylphenol. BACKGROUND
[0002] In recent years, with the increasing demand for energy and the depletion of fossil energy and the deterioration of the ecological environment, the development of biomass energy has become an inevitable choice. Lignin accounts for 30-40% of the mass of biomass, and is favored by the world due to its abundant and stable supply, not competing with people for food, not competing with food for land and other advantages.
[0003] Through the reduction catalytic fractionation technology, natural lignin can be efficiently depolymerized into a limited number of methoxylated alkyl phenols. Further catalytic conversion of the products of the above-mentioned reduction catalytic fractionation technology can produce important bulk chemicals and fuels such as high-value-added alkyl phenols, aromatic hydrocarbons and naphthenes.
[0004] 4-propylguaiacol is one of the most representative phenolic monomers in the reduction catalytic fractionation products. How to produce 4-propylphenol from 4-propylguaiacol is an important research topic.
[0005] Copper molybdate (CuMoO4) is a low-cost, non-toxic molybdate. Its unique physical and chemical properties have attracted widespread attention in many fields such as catalysis, optoelectronics, supercapacitors, etc. On the one hand, at present, copper molybdate is mainly prepared by hydrothermal method, coprecipitation method and sol-gel method. These methods are relatively complex, low in preparation efficiency, not environmentally friendly and economically unprofitable. On the other hand, how to use the prepared copper molybdate as a catalyst to catalyze the demethoxylation of 4-propylguaiacol to better produce 4-propylphenol is still a problem to be considered. SUMMARY
[0006] Therefore, one object of the present application is to provide a preparation method of a copper molybdate catalyst for catalyzing the demethoxylation of 4-propylguaiacol, which is simpler in operation, uses fewer types of solvents and more environmentally friendly solvents. Further, the prepared copper molybdate catalyst can be used to catalyze the demethoxylation of 4-propylguaiacol to produce 4-propylphenol, which has high conversion rate and selectivity and good stability. Another object of the present application is to provide a copper molybdate catalyst prepared by the above-mentioned preparation method. Still another object of the present application is to provide an application of the above-mentioned copper molybdate catalyst. Yet another object of the present application is to provide a method for producing 4-propylphenol from 4-propylguaiacol.
[0007] The above objects of the present application are achieved by the following technical solutions.
[0008] On one hand, the present invention provides a method for preparing a copper molybdate catalyst for catalyzing the demethoxylation of 4-propylguaiacol, comprising the following steps:
[0009] A water-soluble molybdate and a water-soluble copper salt are mixed with water to obtain a metal aqueous solution. The metal aqueous solution is then concentrated, dried, and calcined to obtain a catalyst. This preparation method is simpler to operate, uses only water as a solvent, making it more environmentally friendly, and the resulting copper molybdate catalyst results in a high conversion rate of 4-propylguaiacol and a high selectivity for the product 4-propylphenol.
[0010] The present invention has surprisingly discovered that the order in which water-soluble molybdate, water-soluble copper salt, and water are mixed is crucial. Only by dissolving the water-soluble molybdate in water first, and then adding the water-soluble copper salt to dissolve it, can the catalytic performance of the resulting catalyst be better.
[0011] In this invention, the water-soluble molybdate is ammonium molybdate. Ammonium molybdate can be diammonium molybdate, tetraammonium molybdate, or heptamolybdate, preferably heptamolybdate. Ammonium molybdate may or may not contain water of crystallization. According to one embodiment of the invention, the water-soluble molybdate is ammonium heptamolybdate tetrahydrate. The water-soluble copper salt is selected from copper chloride and copper nitrate, preferably copper nitrate. The water-soluble copper salt may or may not contain water of crystallization. According to one embodiment of the invention, the water-soluble copper salt is copper nitrate trihydrate.
[0012] In this invention, the amount of water used is sufficient to completely dissolve both the water-soluble molybdate and the water-soluble copper salt, resulting in a clear aqueous metal solution. The ratio of the volume of water to the sum of the masses of the water-soluble molybdate and the water-soluble copper salt is (20–120) mL:6 g. For example, it can be 55 mL:6 g, 75 mL:6 g, or 100 mL:6 g.
[0013] In this invention, the molar ratio of molybdenum in the water-soluble molybdate to copper in the water-soluble copper salt is 1:1. This results in a copper molybdate catalyst with higher purity and better catalytic performance.
[0014] In this invention, the concentration is carried out under reduced pressure to remove water. Preferably, this invention uses rotary evaporation to prepare the CuMoO4 catalyst, which, through a simple and environmentally friendly step, establishes a strong interaction between Cu and Mo. This is beneficial for the formation of a uniformly dispersed and high-proportion Cu in the reduced catalyst. 0 and Mo 0 Active site, Cu 0 As an active site for H2 dissociation, it can inhibit coking and promote demethoxylation reactions, thereby improving the stability and conversion rate of the catalyst. Compared to MoO2, Mo... 0 As an active site that is more conducive to CO bond breaking, Mo 0The more the proportion is, the more beneficial to the demethoxylation reaction and the inhibition of the side reaction of hydrodeoxygenation, and then the conversion rate and selectivity of the catalyst are improved.
[0015] According to the preparation method, preferably, the water-soluble molybdate is ammonium molybdate; the water-soluble copper salt is selected from one of copper chloride and copper nitrate; and the molar ratio of the molybdenum element in the water-soluble molybdate to the copper element in the water-soluble copper salt is 1:1.
[0016] According to the preparation method, preferably, the water-soluble molybdate is dissolved in water to obtain a first solution; and then the water-soluble copper salt is dissolved in the first solution to obtain the metal aqueous solution. The dissolving can be carried out at room temperature. When mixing, stirring is carried out, and the stirring time is not more than 1 h. In this way, the copper molybdate catalyst with better catalytic performance can be obtained.
[0017] According to the preparation method, preferably, the concentration is rotary evaporation under reduced pressure. In the present application, rotary evaporation is carried out by using a rotary evaporator. The manufacturer and model of the rotary evaporator are not particularly limited. The temperature during rotary evaporation can be 40-55℃, and preferably 50-55℃. The rotation speed during rotary evaporation can be 100-150 rpm. The vacuum pressure value during rotary evaporation can be 20-30 mbar, for example, 25 mbar.
[0018] According to the preparation method, preferably, the drying is carried out at 50-80℃ for 3-6 h. The temperature during drying can be 50-80℃, and preferably 55-70℃, for example, 60℃. The time during drying can be 3-6 h, and preferably 4-5 h.
[0019] According to the preparation method, preferably, the calcination is carried out at 300-800℃ for 1.5-3.5 h. The temperature during calcination can be 300-800℃, and preferably 500-800℃. The time during calcination can be 1.5-3.5 h, and preferably 2-2.5 h.
[0020] In another aspect, the present application further provides a copper molybdate catalyst for catalyzing the demethoxylation of 4-propyl guaiacol to produce 4-propyl phenol, which is prepared according to the preparation method as described above.
[0021] In yet another aspect, the present application further provides the use of the copper molybdate catalyst as described above for catalyzing the demethoxylation of 4-propyl guaiacol to produce 4-propyl phenol.
[0022] In still another aspect, the present application also provides a method for producing 4-propylphenol from 4-propylguaiacol, comprising the following steps: loading the copper molybdate catalyst as described above into a fixed bed reactor, and activating the catalyst under hydrogen atmosphere; and then feeding 4-propylguaiacol into the fixed bed reactor under hydrogen atmosphere, at a temperature of 295-360°C and without adding any solvent, to perform the demethoxylation reaction, so as to obtain 4-propylphenol. Such a method has milder reaction conditions, high conversion rate of the raw material 4-propylguaiacol, and high selectivity of the product.
[0023] In the present application, the activation temperature of the copper molybdate catalyst is 500-600°C, preferably 510-580°C, for example 510°C, 520°C, 530°C, 550°C, 560°C, or 580°C. The activation time of the copper molybdate catalyst can be 0.5-1.5h, preferably 1-1.5h. The hydrogen flow rate can be 30-60mL / min, preferably 45-55mL / min, for example 50mL / min. Since the present application uses a fixed bed reactor, the amount of the copper molybdate catalyst can be calculated according to the mass space velocity. When scaling up the production, the amount of the copper molybdate catalyst can be determined according to the hourly feed amount of 4-propylguaiacol and the mass space velocity at which the yield of 4-propylphenol is the highest. According to a specific embodiment of the present application, the mass space velocity of the copper molybdate catalyst of the present application at which the yield of 4-propylphenol is the highest is 7h -1 .
[0024] According to the method of the present application, preferably, the activation temperature of the catalyst is 500-600°C; and the feed rate of 4-propylguaiacol is 500-6000μL / min.
[0025] In the present application, the feed rate of 4-propylguaiacol can be 500-6000μL / min, preferably 1200-6000μL / min. For example, it can be 1942μL / min, 3236μL / min, 4530μL / min, 5178μL / min, or 5825μL / min.
[0026] The temperature for the demethoxylation reaction of 4-propylguaiacol can be 295-360°C, preferably 300-360°C. For example, it can be 310°C, 330°C, or 350°C. During the reaction, the hydrogen flow rate can be 30-60mL / min, preferably 45-55mL / min, for example 50mL / min. The reaction is under normal pressure (0.1MPa).
[0027] The application also finds that if a non-noble metal catalyst such as cobalt-nickel is used as a catalyst in a continuous reaction using a fixed bed reactor, the stability is not good, the conversion rate is obviously reduced after long time use, and some need to add solvent, some have too high metal loading, and some catalysts have limited processing capacity. The stability of the copper molybdate catalyst prepared by the application is better when used in a fixed bed reactor, and under the condition of high mass space velocity, the conversion rate of the raw material and the selectivity of the product are still high, and no solvent needs to be added.
[0028] The preparation method of the copper molybdate catalyst of the application is simpler to operate and more environmentally friendly to use water as a solvent; the obtained catalyst has better catalytic performance and good stability. The method for producing 4-propylphenol from 4-propylguaiacol of the application uses a fixed bed reactor, the reaction conditions are milder, the conversion rate of the raw material is higher, and the selectivity of the product is higher. BRIEF DESCRIPTION OF DRAWINGS
[0029] Figure 1 XRD results of Examples 1 to 5 and XRD results of Comparative Examples 2 and 3.
[0030] Figure 2 Mo 3d XPS fitting results of the activated catalyst of Examples 1, 3, 5, Comparative Example 2 and Comparative Example 3.
[0031] Figure 3 Stability test results of Examples 1, 5, Comparative Example 2 and Comparative Example 3. DETAILED DESCRIPTION
[0032] The application will be further described below in conjunction with specific examples, but the scope of protection of the application is not limited thereto.
[0033] In the following examples, the ammonium heptamolybdate used is ammonium heptamolybdate tetrahydrate (NH4)6Mo7O 24 4H2O, and the copper nitrate used is copper nitrate trihydrate Cu(NO3)2·3H2O.
[0034] In the following examples, the chromatographic column used for GC-FID analysis is: HP-5 column, 50m x 0.32mm x 0.50μm. Programmed temperature is used, from 50℃ to 280℃ at a rate of 10℃ / min; the temperature of the detector: 280℃; column flow rate: 3mL / min; detector type: FID.
[0035] Example 1
[0036] Dissolve 2.497 g of ammonium heptamolybdate and 3.417 g of copper nitrate in 100 mL of water in sequence, i.e. dissolve ammonium heptamolybdate first to obtain a first solution; then add copper nitrate to the first solution to dissolve, and continue to stir at room temperature until the mixture is uniform to obtain a metal aqueous solution.
[0037] Perform rotary evaporation on the metal aqueous solution at 25 mbar, 50°C and 100 rpm to remove water to obtain an initial solid.
[0038] Place the initial solid in a drying box and dry at 60°C for 4 h, and then grind to obtain a powder.
[0039] Place the powder in a muffle furnace and calcine at 800°C for 2 h to obtain a copper molybdate catalyst, which is denoted as CuMoO4-800.
[0040] The CuMoO4-800 catalyst is used in the demethoxylation of 4-propylguaiacol to generate 4-propylphenol:
[0041] Take 40 mg of the copper molybdate catalyst prepared above and load into a fixed bed reactor, reduce at 580°C under a pure H2atmosphere (hydrogen flow rate is 50 mL / min) for 1 h to activate the catalyst. Cool to 310°C, and use a peristaltic pump to feed 4-propylguaiacol at a feed rate of 3236 μL / min, collect the reaction product in a condenser every 1 h with 20 mL of ethyl acetate, and then perform off-line analysis with GC-FID. The analysis results at the 4th h are shown in Table 1.
[0042] Examples 2 to 5
[0043] The difference from Example 1 is only in the calcination temperature. The parameters and analysis results are shown in Table 1. The catalyst obtained in Example 2 is denoted as CuMoO4-700; the catalyst obtained in Example 3 is denoted as CuMoO4-600; the catalyst obtained in Example 4 is denoted as CuMoO4-500; and the catalyst obtained in Example 5 is denoted as CuMoO4-400.
[0044] Comparative Example 1
[0045] Calcine copper nitrate at 600°C for 2 h to obtain a CuO catalyst.
[0046] The CuO catalyst is used in the demethoxylation of 4-propylguaiacol to generate 4-propylphenol, and the reaction conditions are the same as those in Example 1. The analysis results at the 4th h are shown in Table 1.
[0047] Comparative Example 2
[0048] Ammonium heptamolybdate was calcined at 600℃ for 2h to produce MoO3 catalyst. Denoted as MoO3.
[0049] MoO3 catalyst was used to de-methoxylate 4-propyl guaiacol to produce 4-propyl phenol under the same reaction conditions as in Example 1. The analysis results at 4h are shown in Table 1.
[0050] Comparative Example 3
[0051] Copper nitrate and ammonium heptamolybdate were calcined at 600℃ for 2h respectively to produce CuO and MoO3 respectively. MoO3 and CuO were mixed and ground thoroughly to produce MoO3+CuO catalyst. Denoted as MoO3+CuO.
[0052] MoO3+CuO catalyst was used to de-methoxylate 4-propyl guaiacol to produce 4-propyl phenol under the same reaction conditions as in Example 1. The analysis results at 4h are shown in Table 1.
[0053] Comparative Example 4
[0054] 3.417g of copper nitrate and 2.497g of ammonium heptamolybdate were dissolved in 100mL of water in sequence, i.e. copper nitrate was dissolved first, then ammonium heptamolybdate was added to dissolve, after complete dissolution, the mixture was continuously stirred at room temperature until homogeneous. The metal aqueous solution was obtained. The remaining steps and conditions were the same as in Example 1. The analysis results at 4h are shown in Table 1.
[0055] Table 1
[0056]
[0057] In addition, the XRD results of Examples 1 to 5 and the XRD results of Comparative Examples 2 and 3 are shown in Figure 1 The XRD patterns show that copper molybdate was successfully synthesized in Examples 1 to 5.
[0058] The Mo 3d XPS fitting results of the activated catalysts of Example 1, Example 3, Example 5, Comparative Example 2 and Comparative Example 3 are shown in Figure 2 The XPS results show that after reduction, the catalyst calcined at 800℃ has the highest proportion of zero-valent Mo.
[0059] The gas chromatography peak time (i.e. retention time) of Example 1 at 4h is shown in Table 2.
[0060] Table 2
[0061]
[0062] The stability test results of Example 1, Example 5, Comparative Example 2 and Comparative Example 3 are shown inFigure 3 Stability experiment: 40 mg of catalyst prepared in Example 1, Example 5, Comparative Example 2, Comparative Example 3, respectively, was charged into a fixed bed reactor, and reduced at 580°C under a pure H2(50 mL / min) atmosphere for 1 h to activate the catalyst; then, the temperature was lowered to 310°C, and 4-propylguaiacol was added to the fixed bed reactor at a feed rate of 3236 μL / min under normal pressure, in the absence of any solvent and under a hydrogen atmosphere (50 mL / min) using a peristaltic pump, and reacted for 24 h, during which the reaction product was collected every 1 h with 20 mL of ethyl acetate. After the reaction, the catalyst was regenerated by calcination at 550°C under a pure O2for 6 h, and the regenerated catalyst was used as the catalyst to determine the catalyst performance for 24 h.
[0063] Example 6
[0064] The same as Example 1 except for the following differences: in Example 6, the activation temperature of the catalyst was 550°C. The analysis results at the 4th h are shown in Table 3.
[0065] Example 7
[0066] The same as Example 1 except for the following differences: in Example 7, the reaction temperature of the demethoxylation reaction of 4-propylguaiacol was 330°C.
[0067] Example 8
[0068] The same as Example 1 except for the following differences: in Example 8, the reaction temperature of the demethoxylation reaction of 4-propylguaiacol was 350°C.
[0069] Example 9
[0070] The same as Example 1 except for the following differences: in Example 9, the feed rate of 4-propylguaiacol was 1942 μL / min.
[0071] Example 10
[0072] The same as Example 1 except for the following differences: in Example 10, the feed rate of 4-propylguaiacol was 4530 μL / min.
[0073] Example 11
[0074] The same as Example 1 except for the following differences: in Example 11, the feed rate of 4-propylguaiacol was 5178 μL / min.
[0075] Example 12
[0076] The same as Example 1 except for the following difference: In Example 12, the feed rate of 4-propylguaiacol was 5825 μL / min.
[0077] Example 13
[0078] The same as Example 1 except for the following difference: In Example 13, the activation temperature of the catalyst was 500°C.
[0079] Comparative Example 5
[0080] The same as Example 1 except for the following difference: In Comparative Example 5, the activation temperature of the catalyst was 450°C.
[0081] Comparative Example 6
[0082] The same as Example 1 except for the following difference: In Comparative Example 6, the activation temperature of the catalyst was 400°C.
[0083] Comparative Example 7
[0084] The same as Example 1 except for the following difference: In Comparative Example 7, the reaction temperature of the demethoxylation reaction of 4-propylguaiacol was 270°C.
[0085] Comparative Example 8
[0086] The same as Example 1 except for the following difference: In Comparative Example 8, the reaction temperature of the demethoxylation reaction of 4-propylguaiacol was 290°C.
[0087] In Examples 6 to 13 and Comparative Examples 5 to 8, the analysis results at the 4th hour are shown in Table 3.
[0088] Table 3
[0089]
[0090] As shown in Tables 1 and 3, in the fixed bed continuous reaction of the present application, the conversion of the raw material 4-propylguaiacol can reach 99% and the selectivity of the product 4-propylphenol can reach 88% at the 4th hour.
[0091] The present application is not limited to the above-described embodiments, and any modification, improvement, or substitution conceived by those skilled in the art without departing from the essential content of the present application falls within the scope of the present application.
Claims
1. A method for preparing a copper molybdate catalyst for catalyzing demethoxylation of 4-propylguaiacol, characterized by, The method comprises the following steps: Mixing a water-soluble molybdate, a water-soluble copper salt and water to obtain a metal aqueous solution; concentrating, drying and calcining the metal aqueous solution to obtain the copper molybdate catalyst.
2. The production method according to claim 1, characterized by, The water-soluble molybdate is ammonium molybdate; the water-soluble copper salt is selected from one of copper chloride and copper nitrate; the molar ratio of molybdenum in the water-soluble molybdate to copper in the water-soluble copper salt is 1:
1.
3. The production method according to claim 1, characterized by, First, dissolve the water-soluble molybdate in water to obtain a first solution; then dissolve the water-soluble copper salt in the first solution and mix to obtain the metal aqueous solution.
4. The production method according to claim 1, characterized by, The concentration is rotary evaporation under reduced pressure.
5. The preparation method according to claim 1, characterized in that, The drying is drying at 50-80°C for 3-6h.
6. The method of claim 1, wherein, The calcining is calcining at 300-800°C for 1.5-3.5h.
7. A copper molybdate catalyst for catalyzing the demethoxylation of 4-propyl guaiacol to produce 4-propyl phenol, characterized in that, The copper molybdate catalyst is prepared according to the preparation method of claim 1.
8. Use of a copper molybdate catalyst according to claim 7, characterized in that, The copper molybdate catalyst is used for catalyzing demethoxylation of 4-propyl guaiacol to produce 4-propyl phenol.
9. A method for producing 4-propylphenol from 4-propylguaiacol, characterized in that, The method comprises the following steps: loading the copper molybdate catalyst of claim 7 into a fixed bed reactor, activating the catalyst under a hydrogen atmosphere; then feeding 4-propyl guaiacol into the fixed bed reactor under a hydrogen atmosphere, at 295-360°C and without adding any solvent, to carry out demethoxylation reaction and obtain 4-propyl phenol.
10. The method of claim 9, wherein, The activation temperature of the catalyst is 500-600°C; the feeding speed of 4-propyl guaiacol is 500-6000μL / min.